let points = document.getElementsByTagName('li');
for (let i = 0; i < points.length; i++) {
    let point = points[i];
    point.onmouseover = function () {
        for (let j = 0; j < points.length; j++) {
            points[j].style.background = 'white';
        }
        point.style.background = 'red';
    }
}